Instrumentation and techniques of high resolution mass spectrometry are being developed and employed for studying problems of structure, biosynthesis, and drug metabolism, with special attention directed toward antibiotics (especially peptide, polyene and ansamycin antibiotics), biological active marine natural products, nucleosides, alkaloids, and methylphenidate. These techniques include field desorption mass spectrometry (at high and low resolution), especially at high masses, and gas chromatography-mass spectrometry (at high and low resolution); utilizing electron impact, field ionization and chemical ionization; employing capillary as well as conventional columns). BIBLIOGRAPHIC REFERENCES: R.C. Pandey and K.L. Rinehart, Jr., "Polyene Antibiotics. VIII. The Structure of Rimocidin," J. Antibiot., in press (1977). K.L. Olson, K.L. Rinehart, Jr., J.C. Cook, "Phosphazenes: High Molecular Weight Reference Compounds for Field Desorption Mass Spectrometry," Biomed. Mass Spectrom. in press (1977).